System and process for fabricating photovoltaic cell

ABSTRACT

A substrate processing system includes a source unit configured to supply a deposition material to a substrate, a substrate holder configured to hold a substrate to receive the deposition material, a shadow mask comprising a frame that includes two opposing arms; and a crossbar configured to be mounted to the two opposing arms. The frame and the crossbar define a plurality of openings that allow the deposition material supplied by the source unit to be deposited on the substrate. A transport mechanism can produce relative movement between the shadow mask and the substrate.

This application claims priority to commonly assigned provisional U.S.patent application Ser. No. 60/869,728, entitled “A simplified processflow for thin film photovoltaic solar cell production”, filed Dec. 13,2006, the disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

This application relates to the fabrication of multi-layer thin filmdevices, specifically, the fabrication of photovoltaic cells andmodules.

BACKGROUND

A photovoltaic device converts light into voltage and electricalcurrent. The voltage output of a photovoltaic device depends on itsmaterial composition and device structure. Examples of photovoltaicmaterials include single-crystalline silicon, poly-crystal line silicon,amorphous silicon, CdTe, CuInGaSe, etc., which can be formed in thinfilms. Device structures include single junction or multi-junctiondevices. The maximum voltage achieved for open circuit (i.e. zerocurrent) is between 0.2 volts to 5 volts.

An exemplified single junction photovoltaic cell 100, shown in FIG. 1A,includes a transparent upper electrode 110, a PN junction 120 comprisinga window layer 130 and an absorber layer 140 that are doped by oppositesemiconductor types, a lower electrode 150, and a substrate 155. Thetransparent upper electrode layer 110 is made of a transparentconductive oxide material. Incident light passing through the upperelectrode layer 110 are absorbed by the absorber layer 140, whichproduces electron and hole pairs. A voltage is generated between theupper electrode 110 and the lower electrode 150, which can produce aphotovoltaic current when an electrical load is placed between the twoelectrodes. The substrate 155 can be made of metallic or insulatingmaterial, and can be transparent or opaque.

In another example, referring to FIG. 1B, a photovoltaic cell 160includes a upper electrode 170, a PN junction 175 comprising an absorberlayer 180 and a window layer 185, a lower electrode 190, and a substrate195. The upper electrode 170 is not required to be transparent. Thesubstrate 195 is made of a transparent material such glass. The absorberlayer 180 and the window layer 185 are typically made of oppositelydoped semiconductor materials. The lower electrode layer 190 is made ofa transparent conductive oxide material. Incident light passing throughthe substrate 195 and the lower electrode layer 190 are absorbed by theabsorber layer 180, which produces electron and hole pairs. A voltage isgenerated between the upper electrode 170 and the lower electrode 190,which can produce a photovoltaic current when an electrical load isplaced between the two electrodes.

The photovoltaic cells are connected in series to increase the outputvoltage and to reduce internal power loss caused by heating which isproportional to the square of the total current. Each photovoltaic cellcan constitute a small portion of a solar power module to minimize thetotal current generated. A solar power module, for example, can includeten or more serially connected photovoltaic cells. In oneimplementation, thin-film layers deposited on a substrate of aphotovoltaic device are divided into separate photovoltaic cells. Theupper electrode of a photovoltaic cell is electrically connected to thelower electrode of an adjacent photovoltaic cell, thereby forming asolar power module comprising serially connected photovoltaic cells.

FIGS. 2A and 2B are respectively cross-sectional and perspective viewsof an exemplified solar-cell module 200 comprising three seriallyconnected photovoltaic cells 210, 220, 230 on a substrate 205. Thephotovoltaic cell 210 includes a lower electrode 211 on the substrate205, a PN junction 212, and an upper electrode 213. Similarly, thephotovoltaic cells 220 and 230 include respectively lower electrodes221, 231 on the substrate 205, PN junctions 222, 232 respectively on thelower electrodes 221, 231, and upper electrodes 223, 233 respectively onthe PN junctions 222, 232. The substrate 205 and the lower electrodes211, 221, 231 can be transparent to allow transmission of incident lightto the PN junctions 212, 222, 232. Alternatively, the upper electrodes213, 223, 233 can be made of a transparent conductive material such as aconductive oxide. The upper electrode 223 in the photovoltaic cell 220is connected to the lower electrode 211 in the photovoltaic cell 210.The upper electrode 233 in the photovoltaic cell 230 is connected to thelower electrode 223 in the photovoltaic cell 220.

The manufacturing process for the solar-cell module 200 can includedepositions of multiple layers for the lower electrodes 211, 221, 231,PN junctions 212, 222, 232, and upper electrodes 213, 223, 233. Thelayers can be scribed mechanically, by patterning, or by a laser.

One disadvantage of the above described manufacturing process is that acleaning step is typically needed after each patterning step to removethe debris generated during patterning. Another disadvantage is that thecutting through many layers of the film often causes current leakagebetween layers and electrical shorting of the photovoltaic cells. Yetanother disadvantage of the above described patterning process is thatthe roughness of the cut or etched surface may lead to lower electricalperformance and cause failures in the solar-cell modules. In addition,some conventional solar-cell modules require high transparency for useas windows in buildings. The cost for patterning is high since a largeportion of deposited films has to be removed.

The above described disadvantages can increase manufacturing complexityand costs, or decrease the reliability of the solar-cell modules orphotovoltaic cells. There is therefore a need for a simpler and morereliable system for manufacturing solar-cell modules or photovoltaiccells.

SUMMARY

In one aspect, the present invention relates to a substrate processingsystem including a source unit that can supply a deposition material toa substrate; a substrate holder that can hold a substrate to receive thedeposition material; a shadow mask including a frame that includes twoopposing arms; and a crossbar that can be mounted to the two opposingarms, wherein the frame and the crossbar define a plurality of openingsthat allow the deposition material supplied by the source unit to bedeposited on the substrate; and a transport mechanism that can producerelative movement between the shadow mask and the substrate.

In another aspect, the present invention relates to a shadow mask fordefining deposition patterns on a substrate. The shadow mask includes aframe comprising two opposing arms and a crossbar that can be mounted tothe two opposing arms, wherein the frame and the crossbar define aplurality of openings that can pass a deposition material to asubstrate.

In another aspect, the present invention relates to a method forfabricating a solar-cell module. The method includes positioning ashadow mask over a substrate having a first lower electrode layer and asecond lower electrode layer separated from the first lower electrodelayer, wherein the first lower electrode layer and the second lowerelectrode layer comprise a first conductive material, wherein the shadowmask comprises a first opening over the first lower electrode layer anda second opening over the second electrode layer; depositing one or moresemiconductor materials through the first opening to form a first PNjunction structure on the first lower electrode layer and through thesecond opening to form a second PN junction structure on the secondlower electrode layer; producing a first translation between the shadowmask and the substrate; and depositing a second conductive materialthrough the first opening and the second opening to form a first upperelectrode layer on the first PN junction structure and partially on thesecond lower electrode layer, and to form a second upper electrode layeron the second PN junction structure.

Implementations of the system may include one or more of the following.The substrate processing system of claim 1, wherein the crossbarcomprises an elongated portion and a mounting member at an end of theelongated portion, wherein the mounting member can be mounted to the twoopposing arms. The crossbar can further include a spring that can pullthe mounting member against the one of the two opposing arms to securelymount the crossbar across the two opposing arms. The crossbar caninclude an elongated portion, two mounting members at two ends of theelongated portion, and a spring, wherein the mounting members areconfigured to be respectively mounted to the two opposing arms, whereinthe spring can pull the mounting member against the one of the twoopposing arms to securely mount the crossbar across the two opposingarms. The crossbar can include high temperature alloys such as INCONEL,stainless steel, alloys such as KOVAR which have similar thermalexpansion as substrate such as glass, alloys such as INVAR which havenear zero thermal expansion coefficient in certain temperature range,steel, Titanium, Mo, or W. The frame can include Stainless steel, steel,aluminum, titanium, alloys such as KOVAR which have similar thermalexpansion as substrate such as glass, or alloys such as INVAR which havenear zero thermal expansion coefficient in certain temperature range. Athermal expansion coefficient of the crossbar can be lower than athermal expansion coefficient of the frame. The crossbar can have awidth in a range of about 0.02 millimeter and about 2 millimeters,wherein the shadow mask is positioned at a distance smaller than about 2millimeters from the substrate. The shadow mask and the crossbar can besubstantially co-planar. The shadow mask further can include a pluralityof substantially parallel crossbars mounted across the two opposingarms.

Embodiments may include one or more of the following advantages. Thedisclosed systems and methods provide simpler, cleaner, and morereliable processes for manufacturing solar-cell modules or photovoltaiccells comparing to some conventional manufacturing systems. Thedisclosed systems and methods do not produce debris as in the patterningprocess in some conventional systems, as described above. The disclosedsystems and methods thus can eliminate the cleaning steps for removingthe debris in those conventional systems. The disclosed systems andmethods also do not involve cutting thin film layers as conducted insome conventional systems. The disclosed systems and methods can thusavoid current leakage and electrical shorting in those photovoltaiccells or modules made by conventional systems. Additionally, thedisclosed systems and methods do not include the roughness associatedwith cutting or etching on the surface after patterning in thoseconventional systems. The performance can thus be improved andmanufacturing costs of the solar-cell modules can be reduced using thedisclosed systems and methods.

Another advantage of the disclosed system and methods is that multiplelayers in photovoltaic cells can be fabricated in continuous processing.The modules do not need to be disassembled for patterning andre-assembling for subsequent deposition steps as in some conventionsystems. Manufacturing throughput and cost are thus improved.

The details of one or more embodiments are set forth in the accompanyingdrawings and in the description below. Other features, objects, andadvantages of the invention will become apparent from the descriptionand drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of an exemplified single-junctionphotovoltaic cell.

FIG. 1B is a cross-sectional view of another exemplified single-junctionphotovoltaic cell.

FIG. 2A is a cross-sectional view of an exemplified solar-cell modulecomprising serially connected photovoltaic cells.

FIG. 2B is a perspective view of the exemplified solar-cell module inFIG. 2A.

FIG. 3A is a perspective view of an exemplified substrate processingsystem in accordance with the present specification.

FIG. 3B is a cross-sectional view of an exemplified substrate processingsystem in FIG. 3B.

FIG. 4A is a perspective view of the shadow mask and the substrate inthe substrate processing system of FIGS. 3A and 3B.

FIG. 4B is a cross-sectional view showing the deposition of lowerelectrodes on the substrate using the shadow mask.

FIG. 4C is a cross-sectional view showing the deposition of PN junctionson the lower electrodes and the substrate using the shadow mask.

FIG. 4D is a cross-sectional view showing the deposition of upperelectrodes on the PN junctions, the lower electrodes, and the substrateusing the shadow mask.

FIG. 5A is a perspective view of an exemplified shadow mask compatiblewith the substrate processing system and processes shown in FIG. 3A-4D.

FIG. 5B is a detailed cross-sectional side view of a portion of theshadow mask held by a substrate holder and over a substrate.

FIG. 5C is a perspective view of a crossbar including an integratedspring.

FIG. 5D is a detailed perspective view of the crossbar in FIG. 5C.

FIG. 5E is a perspective view of an edge portion of the shadow maskshown in FIGS. 5A-5B.

FIG. 5F is a detailed perspective cross-sectional view of an edgeportion of the shadow mask shown in FIGS. 5A-5B and 5E.

FIG. 6 is a flow diagram for the substrate processing system andprocesses shown in FIGS. 3A-5F.

DETAILED DESCRIPTION

An exemplified substrate processing system 300, referring to FIGS. 3Aand 3B, includes a chamber 310, a substrate holder 406, a substrate 405held by the substrate holder 406, a shadow mask 440 held over thesubstrate 405, and a source unit 320. The source unit 320 can forexample include a target 330 for providing a material to be deposited onthe substrate 405 and a magnetron 340 configured for providing amagnetic field near a surface of the target 330 where the targetmaterial is sputtered off. The source unit 320 can also include anevaporation source, a sublimation source for physical vapor deposition(PVD), a gas distribution plate or a shower head for chemical vapordeposition. The substrate processing system 300 can further include avacuum pump configured to exhaust air from the chamber 310 to produce avacuum environment suitable for substrate processing. The chamber 310can also be filled with a gas to assist substrate processing. Thesubstrate can be held and transported by a transport mechanism in andout of the chamber 310. The substrate processing system 300 can includea heating mechanism configured to heat the substrate 405 to an elevatedtemperature such as 100 C to 600 C to prepare it for processing.

Referring to FIGS. 4A and 4B, the shadow mask 440 positioned over thesubstrate 405 includes a rigid frame 445 and openings 451, 452, and 453.(For illustration purpose, the dimensions such as the thicknesses of thecrossbars and the rigid frame are not to scale in FIGS. 4A and 4B.) Theopenings 451, 452, and 453 are separated by crossbars 455. The shadowmask 440 and the crossbars 455 can be substantially co-planar andpositioned parallel to the upper surface of the substrate 405. Theopenings 451, 452, and 453 in the shadow mask 440 allow materials fromthe source unit to be deposited on the substrate 405 through whileblocking material deposition by the rigid frame 445 and the crossbars455. The selective blocking of material deposition can produce mutuallyisolated deposition layers on the substrate 405. The shadow mask 440 canbe used alone or in combination with additional mask(s) to definedeposition patterns.

The shadow masks 440 can be formed by a single piece of material or anassembly of multiple components. The frame 445 can be in a form of aclose loop or a partial loop. In some embodiments, the rigid frame 445includes opposing arms 471, 472, which can be substantially parallel toone another. Each of the crossbars 455 is mounted or connected to botharms 471, 472. The crossbars 455 can be substantially parallel to eachother with separation distance ranging from 3 mm to 100 mm. Thecrossbars 455 can have a thickness between 0.02 millimeter and 2millimeter. The crossbars 455 can be formed by wires, strings, or wireswith integrated or attached spring, ribbons, or stripes. The crossbars455 can be made of high temperature alloys such as INCONEL, stainlesssteel, alloys such as KOVAR which have similar thermal expansion assubstrate such as glass, alloys such as INVAR which have near zerothermal expansion coefficient in certain temperature range, steel, Mo,W, Titanium, and other materials. The rigid frame 445 can be made ofmaterials with similar thermal expansion coefficient to that ofsubstrate 405, such that the relative positions among the substrate 405,the frame 445, and the crossbars 455 are substantially unchanged atelevated temperatures. The frame 445 can be made of alloys such as KOVARwhich have similar thermal expansion as substrate such as glass, steel,alloys such as INVAR which have near zero thermal expansion coefficientin certain temperature range, aluminum, titanium or other materials.

The crossbars 455 can be flexible and mounted in tension onto the rigidframe 455 to keep them straight. These crossbars 455 can be fixed on therigid frame 445 by mounting members such as hooks, fasteners, welding,or other means. The cross-sections of the crossbars 455 can be round,square, polygon or other shapes. The crossbars 455 can be mounted in adirection parallel, vertical, or tilted relative to the gravitationdirection.

In some embodiments, an exemplified shadow mask 440 is shown in FIG. 5A.The shadow mask 440 includes a rigid frame 445 that includes two rigidopposing arms 471, 472. A plurality of crossbars 455 are mounted betweenthe two opposing arms 471, 472, which define a plurality of openings451, 452 between the crossbars 455 and the rigid frame 445. Referring toFIG. 5B, the substrate 405 is held by a substrate holder 415. Thesubstrate holder 415 can be held and moved by a transport mechanism inand out of processing chamber 310. The shadow mask 440 is attached tothe substrate holder 415.

Referring to FIGS. 5B-5F, the crossbar 455 includes an elongated portion501, one or two hooks 502 at one or two ends of the elongated portion501, and a spring 503 that integrated with or separated from theelongated portion 501. The crossbar 455 can be mounted on the rigidframe 445 by respectively positioning the hooks 502 into mounting holes512 formed on the outer edges of the opposing arms 471 or 472. Thesprings 503 is stretched to pull the hooks 502 against the outer edgesof the opposing arms 471 or 472, which holds the crossbar 455 securelyto the rigid frame 445. The tension also keeps the crossbar 455 straightand prevents sagging and deformation in the crossbar 455 even atelevated temperatures.

The shadow mask 440 can be attached to the substrate 405 or thesubstrate holder 415 by fasteners, hook, adhesives, magnetic force,gravity or electro static forces. For example, the shadow mask 440 canbe made of magnetic or Ferro-magnetic material, to allow the shadow mask440 to be held against the substrate holder 415 by a magnetic force.

Since some processing of the substrate 405 may be done at elevatedtemperatures, the shadow mask 440 can be made of materials with thermalexpansion rates that match that those of the substrate 405. The relativeposition between substrate 405 and shadow mask 440 can thus bemaintained at various temperatures during the processing. For a glasssubstrate, a material such as Stainless steel, steel, aluminum, alloyssuch as KOVAR which have similar thermal expansion as substrate such asglass, or alloys such as INVAR which have near zero thermal expansioncoefficient in certain temperature range, can be selected for the shadowmask 440. In some embodiments, the material for the crossbars 455 areselected to have a lower thermal expansion rate compared to the rigidframe 445 to keep the crossbar 455 straight during elevated processingtemperatures. That is, the thermal expansion coefficient of thecrossbars 455 is lower than that of the rigid frame 445. For example,the thermal expansion coefficients of the crossbars 455 and the rigidframe 445 can be both positive, with the one for the crossbars 455having a smaller value. In another example, the crossbars 455 have anegative thermal expansion coefficient and the rigid frame 445 has apositive thermal expansion coefficient. As temperature increase in thechamber 310, the rigid frame 445 expands faster than the crossbars 455,thus increasing the tension in the springs 502 built in the crossbars455, which in turn renders stronger forces to hold the crossbars 455 tothe rigid frame 445. In some embodiments, the crossbars 455 with thesprings 502 keep the crossbar 455 in tension and straight when thecrossbars 455 expand more than the frame 445.

The distance d between the shadow mask 440 and the substrate 405 can becontrolled to allow accurate positions of depositions through theopenings 451-453 onto the substrate 405. The distance d can for examplebe set in less than 2 millimeters when the crossbars 455 have widths ina range of about 0.02 millimeter and about 2 millimeters. The relativespace distance d is selected to ensure precise deposition layers andsharply defined edge in the deposition layers on the substrate 405. Insome embodiments, the shadow mask 440 can be held in contact with thesubstrate 405. The crossbars 455, as described above, are fixedlymounted to the rigid frame 445 to prevent relative movement between thecrossbars 455 and the rigid frame 445 during processing of the substrate405. In this way, the shadow mask 440 allows consistent depositionpatterns to be formed on the substrate 405 during different processingsteps.

An advantage of the shadow mask is that the same shadow mask can be usedfor multiple processing steps. Additional shadow masks may be used tofurther restrict the deposition area in some of the steps to avoidshorting between various layers. Referring to FIGS. 4B-4D, and FIG. 6,the substrate 405 is first cleaned (step 610). The substrate 405 can beformed by a transparent material if the incident light to be receivedfrom below for the solar cell module to be formed. The substrate 405 canbe either transparent or opaque if the incident light is to be receivedfrom above. The shadow mask 440 is positioned over the substrate 405(step 620). Lower electrode layers 411, 421, 431 are deposited on thesubstrate 405 (step 630). The lower electrode layers 411, 421, 431 areformed by conductive materials such as conductive oxide materials. Thecrossbars 455 define the gaps separating the lower electrode layers 411,421, 431. The distances between the lower electrode layers 411, 421, 431can be adjusted by selecting the widths of the crossbars 455. The rigidframe 445 defines the outer boundaries of the lower electrode layers411, 421, 431.

A relative movement is next produced between the substrate 405 and theshadow mask 440 in a direction parallel to the surface of the substrate405 (FIG. 4C, step 640). The relative movement can be produced by eithermoving the substrate 405, or the shadow mask 440, or a combinationthereof. For example the shadow mask 440 can be translated in adirection 460 parallel to the upper surface of the substrate 405.

A plurality of PN junction layers 412, 422, and 432 are respectivelydeposited on the lower electrode layers 411, 421, 431 and the substrate405 (FIG. 4C, step 650). The PN junction layers 411, 421, 431 can eachinclude CdS and CdTe, CdS, CuInGaSe, silicon, amorphous silicon, etc.Each PN junction layers 412, 422, or 432 can cover a major portion ofthe corresponding lower electrode layers 411, 421 or 431 while leavingan area 414, 424 or 434 exposed along the edge of the correspondinglower electrode layers 411, 421 or 431.

Another relative movement is next produced between the substrate 405 andthe shadow mask 440 in a direction parallel to the surface of thesubstrate 405 (FIG. 4D, step 660). The relative movement can for examplebe produced by translating the shadow mask 440 in the direction 460parallel to the upper surface of the substrate 405.

A plurality of upper electrode layers 413, 423, 433 are respectivelydeposited on the PN junction layers 412, 422, and 432 and the substrate405 (FIG. 4C, step 670). The upper electrode layers 413, 423, 433 areformed by a conductive material such as a conductive oxide material. Thetranslation of the shadow mask 440 allows the upper electrode layer 413to be partially formed on the surface 424 on the lower electrode layer421, which electrically connects the upper electrode layers 413 and thelower electrode layer 421. Similarly, the upper electrode layer 423 ispartially formed on the surface 434 on the lower electrode layer 431.Photovoltaic cells 410, 420, 430 are thus formed on the substrate 405.The photovoltaic cells 410, 420, 430 are serially connected: the upperelectrode Saver 413 of the photovoltaic cell 410 is connected to thelower electrode layer 421 of the photovoltaic cell 420; the upperelectrode layer 423 of the photovoltaic cell 420 is connected to thelower electrode layer 431 of the photovoltaic cell 430. Externalelectrical connections can be mounted to the lower electrode layer 411and the upper electrode layer 433 for outputting a photovoltaic voltagethat is equal to the sum of voltages produced by the serially connectedphotovoltaic cells 410, 420, 430 (step 680). Finally the seriallyconnected photovoltaic cells 410, 420, 430 are sealed and packaged (step690).

The disclosed systems and methods may include one or more of thefollowing advantages. The disclosed systems and methods provide simpler,cleaner, and more reliable processes for manufacturing solar-cellmodules or photovoltaic cells comparing to some conventionalmanufacturing systems. The disclosed systems and methods do not producedebris as in the patterning process in some conventional systems, asdescribed above. The disclosed systems and methods thus can eliminatethe cleaning steps for removing the debris in those conventionalsystems. The disclosed systems and methods also do not involve cuttingthin film layers as conducted in some conventional systems. Thedisclosed systems and methods can thus avoid current leakage andelectrical shorting in those photovoltaic cells or modules made byconventional systems. Additionally, the disclosed systems and methods donot include the roughness associated with cutting or etching on thesurface after patterning in those conventional systems. The performancecan thus be improved and manufacturing costs of the solar-cell modulescan be reduced using the disclosed systems and methods.

Another advantage of the disclosed system and methods is that multiplelayers in photovoltaic cells can be fabricated in continuous processing.The modules do not need to be disassembled for patterning andre-assembling for subsequent deposition steps as in some conventionsystems. Manufacturing throughput and cost are thus improved.

The disclosed systems and methods may be applied to depositions of asingle thin film, two thin films, and four or more thin films. Forexample, a glass substrate may be supplied a continuous lower electrodebefore photovoltaic cell manufacturing. A laser or mechanical cutting ispreformed to cut the lower electrode layer into separate lowerelectrodes for different photo voltaic cells. A shadow mask patterningis applied to subsequent processing.

It is understood that the disclosed process chamber is compatible withdifferent types of processing operations such as physical vapordeposition (PVD), thermal evaporation, thermal sublimation, sputtering,chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), ion etching, or sputter etching. The shadow mask mayinclude different designs and patterns from the one described above. Forexample, a shadow mask can include non-parallel crossbars. The crossbarscan be secured onto a rigid frame by different arrangements. The shadowmask can include other materials from the examples described above.

1. A substrate processing system, comprising: a source unit configuredto supply a deposition material to a substrate; a substrate holderconfigured to hold a substrate to receive the deposition material; ashadow mask comprising: a frame that includes two opposing arms; and aplurality of crossbars each comprising an elongated portion and amounting member configured to be mounted to one of the two opposingarms, wherein each of the plurality of crossbars comprises a springconfigured to pull the mounting member against the one of the twoopposing arms to securely mount the crossbar across the two opposingarms, wherein the frame and the crossbar define a plurality of openingsthat are configured to pass a deposition material to a substrate; and atransport mechanism configured to produce relative movement between theshadow mask and the substrate.
 2. The shadow mask of claim 1, whereinthe spring and the elongated portion in the at least one of theplurality of crossbars form an integrated component.
 3. The shadow maskof claim 1, wherein the spring, the mounting member, and the elongatedportion in the at least one of the plurality of crossbars form anintegrated component.
 4. The substrate processing system of claim 1,wherein each of the plurality of crossbars comprises an elongatedportion, two mounting members at two ends of the elongated portion, anda spring, wherein the mounting members are configured to be respectivelymounted to the two opposing arms, wherein the spring is configured topull the mounting member against the one of the two opposing arms tosecurely mount the crossbar across the two opposing arms.
 5. Thesubstrate processing system of claim 1, wherein the crossbar comprisesan alloy, stainless steel, steel, Titanium, Mo, or W.
 6. The substrateprocessing system of claim 1, wherein the frame comprises Stainlesssteel, steel, aluminum, titanium, or an alloy.
 7. The shadow mask ofclaim 1, wherein a thermal expansion coefficient of the plurality ofcrossbars is lower than a thermal expansion coefficient of the frame. 8.The shadow mask of claim 1, wherein the plurality of crossbars has awidth in a range of about 0.02 millimeter and about 2 millimeters. 9.The shadow mask of claim 1, wherein the plurality of crossbars aresubstantially parallel to each other.
 10. The shadow mask of claim 9,wherein the plurality of crossbars are perpendicular to the two opposingarms.
 11. A shadow mask for defining deposition patterns on a substrate,comprising: a frame comprising two opposing arms; and a plurality ofcrossbars each comprising an elongated portion and a mounting memberconfigured to be mounted to one of the two opposing arms, wherein eachof the plurality of crossbars comprises a spring configured to pull themounting member against the one of the two opposing arms to securelymount the crossbar across the two opposing arms, wherein the frame andthe crossbar define a plurality of openings that are configured to passa deposition material to a substrate.
 12. The shadow mask of claim 11,wherein the spring and the elongated portion in the at least one of theplurality of crossbars form an integrated component.
 13. The shadow maskof claim 11, wherein the spring, the mounting member, and the elongatedportion in the at least one of the plurality of crossbars form anintegrated component.
 14. The shadow mask of claim 11, wherein each ofthe plurality of crossbars comprises an elongated portion, two mountingmembers at two ends of the elongated portion, and a spring, wherein themounting members are configured to be respectively mounted to the twoopposing arms, wherein the spring is configured to pull the mountingmember against the one of the two opposing arms to securely mount thecrossbar across the two opposing arms.
 15. The shadow mask of claim 11,wherein the crossbar comprises an alloy, stainless steel, steel,Titanium, Mo, or W.
 16. The shadow mask of claim 11, wherein the framecomprises Stainless steel, steel, aluminum, titanium, or an alloy. 17.The shadow mask of claim 11, wherein a thermal expansion coefficient ofthe plurality of crossbars is lower than a thermal expansion coefficientof the frame.
 18. The shadow mask of claim 11, wherein the plurality ofcrossbars has a width in a range of about 0.02 millimeter and about 2millimeters.
 19. The shadow mask of claim 11, wherein the plurality ofcrossbars are substantially parallel to each other.
 20. The shadow maskof claim 19, wherein the plurality of crossbars are perpendicular to thetwo opposing arms.